The present invention relates to an adjustment mechanism for a friction drive unit, especially for a friction drive unit of a vacuum tool of a vacuum cleaner; to adjust the contact pressure between the friction wheel and a cooperating wheel of the friction drive unit, one of the wheels of the friction drive unit is mounted on a lever that is pivotable about a pivot axis.
In a friction drive unit, the peripheral surface of a friction wheel is pressed against the peripheral surface of a cooperating wheel (a drive wheel). The surfaces of the wheels that contact one another are embodied and paired in such a way that a high frictional engagement is achieved in order to obtain an as nonslip a transfer as possible of a maximum torque at a minimum contact pressure.
In order to establish an optimum contact pressure, it is known, for example, to dispose the drive motor of the friction drive unit on an adjustable mounting, with the position of the mounting being adapted to be varied by spring force, set screws, or other adjustment means in such a way that the drive wheel that is secured to &he motor shaft can be pressed against the wheel that is to be driven with that force that is required to transfer the desired torque.
It is also known to shift the spacing of the driven wheel relative to the stationary drive wheel using appropriate adjustment means in order to establish the desired contact pressure for achieving the required frictional engagement.
All of the known adjustment means have very complicated constructions and are complicated to operate. Although these known adjustment means are generally suitable for large industrial applications, they are hardly suitable for small-scale commercial use or for household use. The handling and operation of these known adjustment mechanisms are particularly cumbersome for the ultimate user.
It is therefore an object of the present invention to provide for the pair of wheels of a friction drive unit an adjustment mechanism that has a straightforward construction, is easy to adjust can be mass produced in an economical manner, and ensures a simple handling and operation.